I. Field of the Invention
The present invention relates to a die assembly for forming a bead on a tube.
II. Description of Related Art
There are many applications in which a bead is formed adjacent a free end of the tube. Such beads have an outside diameter greater than the diameter of the tube and such beads are utilized to secure the tube to both flexible hoses as well as to quick connect couplings.
In order to form the bead on the tube, it has been previously known to utilize a die assembly to radially deform and expand the tube to form the bead. These previously known die assemblies typically comprise a holder secured to the tube to prevent axial movement of the tube relative to the holder. A die having a mandrel slidably received within the interior of the tube was aligned with the holder while forming surfaces corresponding to the desired shape of the bead were formed on both the holder as well as the die.
In order to form the bead, the holder and die were moved together thus radially outwardly expanding the tube into the forming surfaces formed on both the holder and the die. In doing so, the forming surface on the die would deform the surface of the bead axially closest to the free end of the tube while, conversely, the forming surface on the holder would form the opposite axial end of the bead.
These previously known die assemblies for forming beads on tubes, however, have not proven wholly satisfactory in operation. One disadvantage of these previously known die assemblies is that during the process of outwardly deforming the tube to form the bead, the outer periphery of the tube between the die and the holder was unconstrained. This, in turn, permitted the tube to radially deform outwardly in an irregular fashion such that it was not possible to maintain close tolerances in the shape or size of the bead.
A still further disadvantage of these previously known die assemblies for forming beads is that, since the outer periphery of the bead between the holder and the die was unconstrained, burrs would form on the outer surface of the bead during the deformation process. Such burrs, however, are unacceptable in many applications and thus require an additional deburring operation to remove the burrs before the tubes can be used in production. Such a deburring process, however, adds both time and cost to the manufacturing process.
The present invention provides a die assembly for forming a bead on a tube which overcomes all of the above-mentioned disadvantages of the previously known devices.
In brief, the die assembly of the present invention comprises a holder which secures the tube against axial movement to the holder such that a portion of the tube protrudes outwardly from one side of the holder along a predetermined axis. This holder, furthermore, includes a forming surface which circumscribes the tube as the tube protrudes outwardly from the holder. In practice, this forming surface is preferably a surface which extends radially outwardly from the tube in a plane generally perpendicular to the tube axis.
The die assembly further comprises a first die part having a cylindrical mandrel with an outside diameter substantially the same as the inside diameter of the tube. Furthermore, the mandrel is coaxially positioned with the predetermined axis and is slidably receivable within the outwardly protruding portion of the tube.
A tubular and cylindrical sleeve is also mounted to the first die so that the sleeve is coaxial with the mandrel. The sleeve has an inside diameter substantially the same as the outside diameter of the tube so that the tube extends between the sleeve and the mandrel. The sleeve also includes a predetermined outer periphery as well as a conical surface coaxially formed around the free end of the sleeve and thus coaxially around the tube.
A second die part has a throughbore complementary in both shape and size to the outer periphery of the sleeve. This second die part is slidably mounted to the first die part along the predetermined axis and is movable between an extended position and a retracted position relative to the first die part. In its extended position, the sleeve is aligned with the second die part throughbore while in its retracted position, the sleeve extends at least partially into the throughbore of the second die part. A spring is disposed between the first and second die parts to resiliently urge the second die part to its extended position.
Any conventional actuator is utilized to secure the tube and move the holder relative to the first die part along the predetermined axis between the first position and the second position. In its first position, the holder abuts against the second die part while the second die part is in its extended position. Conversely, as the holder is moved to its second position relative to the first die part, the holder moves the second die part to its retracted position thus radially outwardly deforming the bead between the forming surface in the holder and the conical surface on the sleeve. Furthermore, since the throughbore formed in the second die part circumscribes and constrains the tube around the bead during the entire formation of the bead, and also since the holder remains in contact with the second die part during the entire deformation process, the bead is not only accurately formed on the tube, but the possibility of a burr forming between the holder and the second die part is altogether eliminated.